Role for complement in mediating intestinal nitric oxide synthase-2 and superoxide dismutase expression

Area of Science:

• Biomedical Science
• Immunology
• Gastroenterology

Background:

• Ischemia-reperfusion (I/R) injury is a significant clinical challenge.
• Inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) are key enzymes implicated in I/R pathology.
• The role of complement component 5 (C5) in modulating these enzymes during gastrointestinal I/R (GI/R) remains unclear.

Purpose of the Study:

• To investigate the effect of complement modulation on iNOS and SOD in a rat model of GI/R.
• To determine if anti-C5 therapy impacts key inflammatory markers and enzyme activity/expression post-GI/R.

Main Methods:

• Rats underwent GI/R injury with administration of an inhibitory anti-C5 antibody (18A) or a non-inhibitory control (16C).
• Intestinal tissue was analyzed for iNOS and SOD (Cu/Zn SOD, Mn SOD) mRNA and protein expression using RT-PCR and immunohistochemistry.
• Nitrotyrosine staining and phosphorylated IkappaB-alpha (p-IkappaB-alpha) levels were assessed to evaluate inflammation and NF-kappaB pathway activation.

Main Results:

• GI/R significantly increased intestinal iNOS mRNA and protein, which was attenuated by anti-C5 treatment.
• While GI/R reduced Cu/Zn SOD activity and Mn SOD protein, anti-C5 therapy preserved these levels.
• Anti-C5 treatment reduced protein nitration and decreased p-IkappaB-alpha expression, indicating reduced inflammation.

Conclusions:

• Complement activation contributes to GI/R injury by upregulating iNOS and downregulating SOD activity and protein.
• Inhibiting C5 with monoclonal antibody 18A ameliorates GI/R-induced tissue damage.
• Anti-C5 therapy offers a potential therapeutic strategy for managing GI/R by mitigating inflammatory responses and oxidative stress.